1. Technical Field
This application is the US national phase of international application PCT/GB03/02528 filed 12 Jun. 2003 which designated the U.S. and claims benefit of EP 02254105.6, dated 12 Jun. 2002, the entire content of which is hereby incorporated by reference.
The present invention relates to a method and apparatus for pre-processing a video sequence and, in particular, to pre-processing a video sequence prior to transmitting it over a packet switched data network using a protocol such as MPG-4.
2. Related Art
A video sequence comprises a sequential series of complete video frames intended to be displayed successively at a predetermined rate. Each frame comprises a matrix of pixels, each of which has, in the case of black and white video, an associated value indicating the brightness of the pixel, or, in the case of colour video, an associated triplet of values which together indicate both the brightness and the colour of each pixel.
A very common type of video sequence is one in which a single object (eg a person) moves in the foreground against a substantially static background. For example, a video teleconference in which two people sit in front of their respective computers with small cameras transmitting to one another video images of their faces (as well as audio information) will typically fall into this category of video sequence.
The present inventor has realised that in video sequences of this type, the most important aspect of the video sequence tends to be the object moving in the foreground. That is to say, inaccuracies, poor rendering or noise (ie a poor signal to noise ratio) tends to be more noticed by a viewer when it occurs within the foreground object.